A pad body having a two-layer structure is known as a cushion material for a vehicle seat. JP-A-2010-125138 discloses a pad body having a two-layer structure in which a front layer pad on a seating surface side is an urethane foam obtained by foam-molding a polyurethane resin and a back layer pad disposed on the side of the front layer pad opposite to the seating surface is a foamed body obtained by foam-molding AS resin (copolymer of styrene and acrylonitrile).
Typically, a die is used for manufacturing the pad body. The die has an upper die and a lower die, and a cavity corresponding to a shape of the pad body is formed between the upper die and the lower die when the upper die is closed with respect to the lower die. A cavity surface of the lower die is formed in a shape corresponding to a shape of a front surface portion side (seating surface side) of the pad body, and a cavity surface of the upper die is formed in a shape corresponding to a shape of a back surface portion side (side opposite to the seating surface) of the pad body. Further, in a state where the back surface of the two-layered pad is temporarily held on the cavity surface of the upper die by mechanical fitting or magnetic force or the like acting between a magnet embedded in the cavity surface of the upper die and an iron member inserted in the two-layered pad, the pad body is manufactured by pouring foamed polyurethane resin raw material onto the cavity surface of the lower die, closing the upper die with respect to the lower die, and performing foam-molding.
In the method for manufacturing the pad body having the two-layered structure disclosed in JP-A-2010-125138, there is a problem that a part of the foamed polyurethane resin raw material intrudes between the cavity surface of the upper die and the back surface of the back layer pad from an end portion of the back surface of the back layer pad in contact with the cavity surface of the upper die and the part is foamed and cured therein in the process of foaming and curing the foamed polyurethane resin raw material. When the part of the foamed polyurethane resin raw material intrudes between the cavity surface of the upper die and the back surface of the back layer pad and the part is foamed and cured therein, a mounting surface of the pad body to a vehicle body and the back surface of the back layer pad do not come into close contact with each other, and a height of the seating surface is deviated from a design value. When attempting to remove the foamed body formed on the back surface of the back layer pad in order to avoid such a situation, there is a problem that the number of working steps is increased.